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Unlike F350/450/SuperDuty chassis, Ford does not provide a 12V charge line on the F53 platform. That is left up to the "body builder" (i.e., coach manufacturer).
You can dig some information out of the
Body Builders Layout Books, but no diagrams for the F53 are there (usually). For them you need the Ford maintenance manual for your year chassis. I have a DVD for mine.
Winnebago has put many of it wiring diagrams
on line.
I'd call Winnebago and ask them where the charge line is.
You could also send a private message to Grant Harris (iRV2 user "grtharris"). He's very knowledgeable about Ford and Winnebago Fords in particular. Here's
one of his posts that may help you.